Power management for power-over-ethernet-capable switch

ABSTRACT

A system and method is described that allows a PoE-capable switch to selectively provide power to one or more remote devices in an instance where power being supplied to the switch itself is limited or failing. In one embodiment, the switch receives a notification from an uninterruptable power supply (UPS) and, in response to receiving the notification, selectively provides power to one or more devices powered by the switch. Selectively providing power to one or more of the devices may include providing power to only a subset of the devices, providing a different amount of power to different ones of the devices, or providing power for different durations to different ones of the devices. In an alternate embodiment, in response to receiving the notification, the switch communicates with a remote device and causes the remote device to activate at least one power saving feature.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.11/752,952, filed May 24, 2007, the entirety of which is incorporated byreference herein.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention generally relates to networks in which power is deliveredusing Power over Ethernet (PoE) technology. More specifically, theinvention is related to a system and method that allows a PoE-capableswitch to selectively provide power to one or more remote devices in aninstance where the power being supplied to the switch itself is limitedor failing.

2. Background

Power over Ethernet (PoE) technology enables the transmission ofelectric power, along with data, to remote devices over standardtwisted-pair cable in an Ethernet network. This technology is commonlyused for powering Voice over Internet Protocol (VoIP) telephones,wireless local area network (WLAN) access points, webcams, embeddedcomputers, and other appliances where it would be inconvenient orinfeasible to supply power separately. The technology works with anunmodified Ethernet cabling infrastructure. The current industrystandard for PoE technology is the IEEE 802.3af standard, althoughproprietary PoE systems exist as well.

A conventional PoE-capable switch is able to detect whether a deviceconnected to one of its ports is capable of being powered via theEthernet cable and to supply power to the device accordingly. However,such a switch is not capable of selectively providing power to one ormore devices powered by the switch in an instance where the supply ofpower to the switch is limited or failing. This issue will be furtherexplained with reference to FIG. 1 and FIG. 2.

FIG. 1 illustrates a conventional network system 100 in which aPoE-capable switch 102 is used to transfer data between a local areanetwork 104 and a plurality of remote devices 106, as well as to providepower to those devices. As noted above, each of powered devices 106 maybe one of a VoIP telephone, WLAN access point, webcam, embeddedcomputer, or other appliance adapted to receive both data and power viaa standard Ethernet cable. In network system 100, switch 102 is poweredby AC power supplied by a local utility. When the AC power supply toswitch 102 is shut off, as in the case of a power outage, switch 102will shut down, thereby also depriving devices 106 of power. This may beextremely disruptive to the users of devices 106. For example, in aninstance where a device 106 is a VoIP telephone, loss of power in thismanner may lead to the unexpected termination of an active telephoneconversation.

A conventional method for dealing with the foregoing issue is to placean uninterruptable power supply (UPS) between the utility power supplyand the PoE-capable switch. Such an approach is depicted in networksystem 200 of FIG. 2. As shown in FIG. 2, a UPS 208 has been connectedbetween the utility power supply and PoE-capable switch 102. In aninstance where the utility power supply is shut off, UPS 208 can providebattery-supplied power to switch 102 until AC power from the utility isrestored or until the UPS battery or batteries are depleted, whicheveroccurs first. Consequently, switch 102 can continue to provide power todevices 106 at least until the battery-supplied power runs out.

However, during the time that switch 102 is running off of UPS batterypower, switch 102 is not aware that the utility power supply has failedand that the UPS batteries are now the primary source of power. As aresult, switch 102 continues to provide power to all devices 106,whether such devices are critical or non-critical, as it normally would.By consuming power in this fashion, switch 102 and all devices 106 donot stay up very long. Furthermore, when power runs out, switch 102 andall devices 106 (whether critical or not) turn off simultaneously andwithout regard to priority. Where switch 102 requires a large powersupply, the only way to avoid these issues is to install a very largeUPS and optionally a generator between the utility power supply andswitch 102, such that secondary power can be provided to switch 102 evenduring very long power outages. This is a costly proposition.

The issue of managing power delivered to a PoE switch that then deliverspower to devices at the edge of network is becoming a critical one. Thisis due to rapid growth in the deployment of IP telephones, wirelessaccess points, video cameras, and other devices that leverage PoEcapabilities. This problem will be exacerbated in the future as more andmore devices and systems are designed that rely on PoE technology. Inaccordance with the current 802.3af standard, 48 volts of DC power areprovided over two out of four available pairs on a Category 3/Category 5Ethernet cable with a maximum current of 400 milliamperes for a maximumload power of 15.4 watts. However, a future standard, commonly referredto as PoE+, is presently under development. This draft standarddescribes extending PoE technology by using all four pairs of standardEthernet Category 5 cable to provide up to 56 watts of power. The higherpower available with this future standard should make it possible toprovide power to equipment with higher power requirements, such as WiMAXtransmitters, pan-tilt-zoom cameras, IP-videophones and thin clients.

What is needed, then, is a system and method that would allow aPoE-enabled Ethernet switch to receive a notification from a UPS that aprimary power source has failed such that the switch can selectivelyprovide power to one or more of devices powered by the switch during thetime that switch is running off of a secondary power source. Forexample, it would be beneficial if such a switch could selectivelyprovide power to only those powered devices that are deemed critical andreduce or turn off power to those powered devices that are deemednon-critical in response to receiving such a notification from the UPS.This would allow the switch to provide power to the critical devices fora longer period of time in a manner that does not require investment ina larger, more expensive secondary power source.

BRIEF SUMMARY OF THE INVENTION

The present invention provides a system and method that allows aPoE-capable switch to selectively provide power to one or more remotedevices in an instance where power being supplied to the switch itselfis limited or failing. In one embodiment of the present invention, theswitch receives a notification from an uninterruptable power supply(UPS) that a primary power source has failed and, in response toreceiving the notification, selectively provides power to one or moredevices powered by the switch during the time that switch is running offof a secondary power source.

For example, in one embodiment of the present invention, the switchselectively provides power to only powered devices that are deemedcritical and reduces or turns off power to powered devices that aredeemed non-critical in response to receiving the notification from theUPS. This allows the switch to provide power to the critical devices fora longer period of time in a manner that does not require investment ina larger, more expensive secondary power source. Other methods forselectively providing power to the powered devices are described herein.

In particular, an embodiment of the present invention is a method forperforming power management by a PoE-capable switch. The PoE-capableswitch is connected to a plurality of remote devices over respectiveEthernet cables and is operable to provide both data and power to eachof the plurality of remote devices over the same Ethernet cable. Themethod includes receiving a notification indicating that a power sourceof the PoE-capable switch is limited or failing, and responsive toreceiving the notification, selectively providing power to one or moreof the plurality of remote devices connected to the PoE-capable switch.

Receiving the notification may include receiving a notification from anuninterruptable power supply (UPS). Selectively providing power to oneor more of the plurality of remote devices connected to the PoE-capableswitch may include providing power to only a subset of the plurality ofremote devices connected to the PoE-capable switch, providing adifferent amount of power to different ones of the plurality of remotedevices connected to the PoE-capable switch, and/or providing power fordifferent durations to different ones of the plurality of remote devicesconnected to the PoE-capable switch. Selectively providing power to oneor more of the plurality of remote devices connected to the PoE-capableswitch may be based on preconfigured data associated with one or moreports of the PoE-capable switch and/or on state information associatedwith one or more of the remote devices.

Another embodiment of the present invention is a PoE-capable switch. ThePoE-capable switch includes a plurality of ports, PoE logic connected tothe plurality of ports, control logic connected to the PoE logic, and adata interface connected to the control logic. Each of the plurality ofports is adapted for connection to a remote device via a respectiveEthernet cable. The PoE logic is controllable to provide power toselected ones of the plurality of ports for delivery to a remote deviceconnected thereto. The control logic is configured to control theoperation of the PoE logic. The data interface is configured to receivea notification indicating that a power source of the PoE-capable switchis limited or failing. The control logic includes power management logicthat is configured to control the PoE logic to selectively provide powerto the plurality of ports responsive to receipt of the notification bythe data interface.

The data interface may comprise a wired interface, such as an RS232interface, a universal serial bus (USB) interface, or an Ethernetinterface, a wireless interface such as any IEEE 802.11 interface or aBluetooth® interface, or any other standard or proprietary wired orwireless interface. The power management logic may be configured tocontrol the PoE logic to provide power to only a subset of the pluralityof ports, to provide a different amount of power to different ones ofthe plurality of ports, and/or to provide power for different durationsto different ones of the plurality of ports. The power management logicmay be configured to control the PoE logic to selectively provide powerto the plurality of ports based on preconfigured data associated withone or more of the plurality of ports and/or on state informationassociated with one or more of remote devices connected to the pluralityof ports. In an alternate embodiment, the power management logic residesin an external server communicatively connected to the PoE-capableswitch or is distributed among the external server and the PoE-capableswitch.

A further embodiment of the present invention is a method for performingpower management by a PoE-capable switch. The PoE-capable switch isconnected to a plurality of remote devices over respective Ethernetcables and is operable to provide both data and power to each of theplurality of remote devices over the same Ethernet cable. The methodincludes receiving a notification indicating that a power source of thePoE-capable switch is limited or failing and, responsive to receivingthe notification, communicating with a selected one of the remotedevices to indicate to the selected remote device to implement at leastone power saving feature supported by the selected remote device.Receiving the notification may include receiving a notification from anuninterruptable power supply (UPS).

A still further embodiment of the present invention is a PoE-capableswitch. The PoE-capable switch includes a plurality of ports, PoE logicconnected to the plurality of ports, control logic connected to the PoElogic, and a data interface connected to the control logic. Each of theplurality of ports is adapted for connection to a remote device via arespective Ethernet cable. The PoE logic is controllable to providepower to selected ones of the plurality of ports for delivery to aremote device connected thereto. The control logic is configured tocontrol the operation the PoE logic. The data interface is configured toreceive a notification indicating that a power source of the PoE-capableswitch is limited or failing. The control logic includes powermanagement logic that is configured to communicate with a remote deviceconnected to one of the plurality of ports to indicate to the remotedevice to implement at least one power saving feature supported by theremote device responsive to receipt of the notification by the datainterface.

The data interface may be a wired interface, such as an RS232 interface,a universal serial bus (USB) interface, or an Ethernet interface, awireless interface such as any IEEE 802.11 interface or a Bluetooth®interface, or any other standard or proprietary wired or wirelessinterface. In an alternate embodiment, the power management logicresides in an external server communicatively connected to thePoE-capable switch or is distributed among the external server and thePoE-capable switch.

Further features and advantages of the invention, as well as thestructure and operation of various embodiments of the invention, aredescribed in detail below with reference to the accompanying drawings.It is noted that the invention is not limited to the specificembodiments described herein. Such embodiments are presented herein forillustrative purposes only. Additional embodiments will be apparent topersons skilled in the relevant art(s) based on the teachings containedherein.

BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES

The accompanying drawings, which are incorporated herein and form partof the specification, illustrate the present invention and, togetherwith the description, further serve to explain the principles of theinvention and to enable a person skilled in the relevant art(s) to makeand use the invention.

FIG. 1 is a block diagram of a prior art network system in which a Powerover Ethernet (PoE)-capable Ethernet switch is powered byutility-supplied AC power.

FIG. 2 is a block diagram of a prior art network system in which aPoE-capable switch is powered primarily by an uninterruptable powersupply (UPS).

FIG. 3 is a block diagram of a network system in accordance with anembodiment of the present invention.

FIG. 4 depicts a flowchart of a method for providing improved powermanagement in a PoE-capable switch in accordance with an embodiment ofthe present invention.

FIG. 5 depicts a flowchart of a method for selectively providing powerto one or more remote devices by a PoE-capable switch based onpre-configured data in accordance with an embodiment of the presentinvention.

FIG. 6 depicts a flowchart of a method for selectively providing powerto one or more remote devices by a PoE-capable switch based on stateinformation in accordance with an embodiment of the present invention.

FIG. 7 depicts a flowchart of a method for selectively providing powerto one or more remote devices by a PoE-capable switch based on bothpre-configured data and state information in accordance with anembodiment of the present invention.

FIG. 8 is a block diagram of a network system in accordance with analternate embodiment of the present invention in which a PoE-capableswitch and remote devices attached thereto jointly participate in apower management function.

FIG. 9 depicts a flowchart of a method for providing improved powermanagement in a PoE-enabled switch in accordance with an embodiment ofthe present invention in which the PoE-capable switch and remote devicesattached thereto jointly participate in a power management function.

FIG. 10 is a block diagram of a network system in accordance with afurther embodiment of the present invention in which the powermanagement function is implemented in a distributed fashion between aPoE-capable switch and a server communicatively coupled thereto.

FIG. 11 is a block diagram of a UPS in accordance with an embodiment ofthe present invention.

FIG. 12 is a block diagram of a PoE-capable switch in accordance with anembodiment of the present invention.

The features and advantages of the present invention will become moreapparent from the detailed description set forth below when taken inconjunction with the drawings, in which like reference charactersidentify corresponding elements throughout. In the drawings, likereference numbers generally indicate identical, functionally similar,and/or structurally similar elements. The drawing in which an elementfirst appears is indicated by the leftmost digit(s) in the correspondingreference number.

DETAILED DESCRIPTION OF THE INVENTION

A. Example Network System in Accordance with an Embodiment of thePresent Invention

FIG. 3 depicts a block diagram of a network system 300 in accordancewith an embodiment of the present invention. As shown in FIG. 3, networksystem 300 includes a PoE-capable switch 302 that is communicativelyconnected to a network 304 and a plurality of remote devices 306 a-306n. In an embodiment, network 304 comprises a local area network (LAN).However, the invention is not limited to LANs, and network 304 maycomprise any type of data communication network that is capable ofcommunicating with a PoE-capable switch.

PoE-capable switch 302 is connected to each of devices 306 a-306 n via aseparate Ethernet cable. PoE-capable switch 302 is adapted to transferdata between network 304 and each of devices 306 a-306 n in a well-knownmanner, as well as to provide power to each of devices 306 a-306 n viathe same Ethernet cable that is used for providing data thereto. In oneembodiment, PoE-capable switch 302 is designed to provide power todevices 306 a-306 n in a manner that is compliant with the IEEE 802.3afstandard. However, the invention is not limited to IEEE802.3af-compliant systems. Rather, the present invention may be used inany network system in which both power and data are provided over anEthernet cable, including but not limited to proprietary PoE systems orsystems that comply with a future IEEE standard that builds on orsupersedes the IEEE 802.3af standard.

Each of remote devices 306 a-306 n is configured to receive both dataand power from PoE-capable switch 302. Each remote device may be any oneof a variety of devices that are designed for use in a PoE system,including but not limited to Voice over Internet Protocol (VoIP)telephones, wireless local area network (WLAN) access points, webcams,embedded computers, WiMAX transmitters, pan-tilt-zoom cameras,IP-videophones, thin clients, or laptop computers. Remote devices 306a-306 n may represent a subset of the remote devices attached toPoE-capable switch 302. In other words, there may be other remotedevices (not shown in FIG. 3) that are connected to switch 302 but arenot capable of receiving power therefrom. Such devices would have theirown local power supplies and therefore would not participate in theimproved power management scheme described herein.

As also shown in FIG. 3, PoE-capable switch 302 is further connected toan uninterruptable power supply (UPS) 308. UPS 308 is adapted to supplypower to switch 302 from a primary power source when the primary powersource is available and to switch to supplying power to switch 302 froma secondary power source when the primary power source becomesunavailable. In system 300, the primary power source is utility-suppliedAC power while the secondary power source is one or more batteriesinternal to UPS 308. However, this example is not intended to limit thepresent invention and other and/or additional power sources may be usedby UPS 308 to provide power to switch 302. For example, UPS 308 may befurther connected to an external power source, such as a generator,battery, or second UPS, and use such external power source when theprimary power source or another secondary power source fails.

As is further shown in FIG. 3, UPS 308 includes status reporting logic320 and switch 302 includes power management logic 322. As will bedescribed in more detail herein, status reporting logic 320 isconfigured to detect when UPS 308 has switched from supplying power toswitch 302 from a primary power source to a secondary power source and,responsive to detecting this, to transmit a notification to switch 302.As also will be described in more detail herein, power management logic322 is configured to selectively provide power to devices 306 a-306 nresponsive to receipt of the notification by switch 302.

B. Example Method for Performing Improved Power Management in aPoE-Capable Switch in Accordance with an Embodiment of the PresentInvention

FIG. 4 illustrates a flowchart 400 of a method for performing improvedpower management in a PoE-capable switch in accordance with anembodiment of the present invention. The method of flowchart 400 willnow be described with further reference to the elements of networksystem 300, described above in reference to FIG. 3, although theinvention is by no means limited to that particular implementation.

As shown in FIG. 4, the method of flowchart 400 begins at step 402 inwhich status reporting logic 320 of UPS 308 detects that UPS 308 hasswitched from supplying power to PoE-capable switch 302 from a primarypower source, such as utility-supplied AC power, to a secondary powersource, such as one or more batteries internal to UPS 308.

At step 404, responsive to detecting that UPS 308 has switched fromsupplying power from a primary to a secondary power source, statusreporting logic 320 transmits a notification to PoE-enabled switch 302.The form and content of this notification will vary depending on theimplementation of UPS 308, switch 302, and the interface between them.As will be appreciated by persons skilled in the relevant art(s), UPS308 and switch 302 may be connected by any of a variety of differentinterfaces for data communication, including but not limited to wiredinterfaces such as an RS-232 interface, a USB interface, or an Ethernetinterface, wireless interfaces such as a BlueTooth® interface or anyIEEE 802.11 interface, or other standard or proprietary wired orwireless interfaces. In one embodiment, the notification is not directlytransmitted from UPS 308 to switch 302, but is instead proxied ortransmitted through one or more intermediate devices such as one or moreservers.

The notification itself may include a very small amount of information,such as an simple indicator signifying that the changeover from primaryto secondary power source has occurred, or may include more information,such as but not limited to a time that the changeover occurred, anamount of power remaining in a secondary power source (e.g., the UPSbattery or batteries), a predicted time that power from the secondarypower source will run out, a predicted time that power from a primarysource will come back on, or the like. The notification may be formattedin accordance with any standard or proprietary network protocol,including but not limited to the TCP/IP protocol or SNMP. Where theamount of information to be sent is significant, packet-basedcommunication in accordance with the TCP/IP protocol may advantageouslybe used to transfer such information from UPS 308 to PoE-capable switch302, although this is a matter of design choice.

The notification may comprise a single message or a plurality ofmessages. The notification may also occur as part of a bilateralcommunication protocol between UPS 308 and switch 302. Furthermore,steps 402 and 404 may be performed automatically by UPS 308 or only inresponse to a query or message from PoE-capable switch 302 or othernetwork entity. In this instance, PoE-capable switch 302 or the othernetwork entity may be deemed the initiator of the method of flowchart400.

At step 406, PoE-capable switch 302 receives the notification from UPS308. As noted above, the form and content of the notification will varydepending on the implementation of UPS 308, switch 302, and theinterface between them.

At step 408, power management logic 322 within switch 302 selectivelyprovides power to one or more of remote devices 306 a-306 n responsiveto receipt of the notification by switch 302. As will be described inmore detail below, the selective providing of power to one or more ofdevices 306 a-306 n by power management logic 322 may includeselectively providing power to only a subset of devices 306 a-306 n,selectively providing different amounts or levels of power to differentones of devices 306 a-306 n, and/or selectively providing power fordifferent durations to different ones of devices 306 a-306 n. Thedetermination of which of devices 306 a-306 n should receive power, theamount of power provided to each device, and the duration over whichpower is provided to each device may be made by power management logic322 based on a variety of factors or inputs, which will also bedescribed in more detail below.

C. Selective Providing of Power by a PoE-capable Ethernet Switch inAccordance with an Embodiment of the Present Invention

As noted above, power management logic 322 within switch 302 isconfigured to selectively provide power to one or more of remote devices306 a-306 n in response to receipt of a notification from UPS 308 byswitch 302. By selectively providing power in this fashion, powermanagement logic 322 is able to reduce the overall power demands onswitch 302 during the time when UPS 308 is providing power from thesecondary power source. Furthermore, by selectively providing power inthis fashion, power management logic 322 is able to use the limitedpower available from the secondary power source in the most effectiveway possible.

FIG. 5 illustrates a flowchart 500 of a method for selectively providingpower to one or more remote devices by a PoE-capable switch inaccordance with an embodiment of the present invention. In theembodiment depicted in FIG. 5, the power management logic within thePoE-capable switch selectively provides power to the one or more remotedevices based on pre-configured data that is associated with each porton the switch. This pre-configured data may be entered by a user andstored in local memory on the switch.

The method of flowchart 500 will now be described with further referenceto the elements of network system 300, described above in reference toFIG. 3, although the invention is by no means limited to that particularimplementation.

The method of flowchart 500 begins at step 502, in which powermanagement logic 322 within switch 302 identifies a particular port onswitch 302. At step 504, power management logic 322 accessespre-configured data that is associated with the identified port. Asnoted above, this pre-configured data may have been previously enteredby a user and stored in a local memory within switch 302.

At step 506, power management logic 322 determines an amount of powerand/or duration that power is to be provided to a device attached to theidentified port based on the pre-configured data. With respect to theamount of power to be provided, the pre-configured data may indicatethat the remote device is to continue to receive the same amount ofpower, a lesser amount of power, or no power at all. With respect to theduration that power is to be provided to the device, the pre-configureddata may indicate that the device is to continue to receive power untilsuch time as UPS 308 can no longer provide power to switch 302, or mayspecify a fixed amount of time that the device is to continue to receivepower from switch 302.

At step 508, switch 302 delivers power to the remote device attached tothe identified port in accordance with the determination(s) made in step506.

It is to be understood that the method of flowchart 500 could beperformed for each port on switch 302 or for only a subset of the portson switch 302.

The foregoing method of flowchart 500 is advantageous because it allowsa user to configure in advance how each port, and therefore each deviceattached to a port, will be supplied power during the time that UPS 308is running off of a secondary power source. The user could thus classifya certain port or class of ports as “critical” and ensure that power isdelivered to devices attached to those ports even when UPS 308 isrunning off of a secondary power source while classifying another portor class of ports as “non-critical” such that devices attached to thoseports receive less or no power during the same time frame. In this way,switch 302 can both conserve power and provide power to critical devicesfor a longer period of time.

The pre-configured data associated with each port may expressly specifythe amount of power and/or the duration that power is to be provided toan attached device. Alternatively, the preconfigured data may indicate aclass or priority level for the port, which is then mapped by powermanagement logic 322 to a particular amount of power and/or durationthat power is to be provided to the attached device. In a still furtherembodiment, power management logic 322 is configured to take intoaccount other or additional pre-configured data associated with theport, such as the type of device attached to the port and the power drawof the device attached to the port, to intelligently determine theamount of power and/or the duration that power is to be provided to adevice attached to the port. Depending on the implementation, the userconfiguration can be very high-level or granular in nature.

FIG. 6 illustrates a flowchart 600 of a method for selectively providingpower to one or more remote devices by a PoE-capable switch inaccordance with an alternate embodiment of the present invention. In theembodiment depicted in FIG. 6, the power management logic within thePoE-capable switch selectively provides power to the one or more remotedevices based on state information obtained for a device attached to agiven port of the switch.

The method of flowchart 600 will now be described with further referenceto the elements of network system 300, described above in reference toFIG. 3, although the invention is by no means limited to that particularimplementation.

The method of flowchart 600 begins at step 602, in which powermanagement logic 322 within switch 302 identifies a particular port onswitch 302. At step 604, power management logic 322 obtains stateinformation associated with a device attached to the identified port.This state information may indicate, for example, whether the deviceattached to the identified port is in an active or an inactive state.For example, if the device is an IP telephone, the state informationmight indicate that the IP telephone is currently being used to handlean active call. Or, for example, if the device is one that can be placedin a powered-up, powered-down, or standby (i.e., power saving) state,such as certain thin clients or laptops, then the state informationmight indicate which of these states that device is currently in. Stateinformation may be obtained from a variety of sources, including but notlimited to the remote device itself, or a server.

At step 606, power management logic 322 determines an amount of powerand/or duration that power is to be provided to the device attached tothe identified port based on the obtained state information. As notedabove, with respect to the amount of power to be provided, the remotedevice may continue to receive the same amount of power, a lesser amountof power, or no power at all. With respect to the duration that power isto be provided, the remote device may continue to receive power untilsuch time as UPS 308 can no longer provide power to switch 302, or mayreceive power for only a fixed amount of time.

At step 608, switch 302 delivers power to the remote device attached tothe identified port in accordance with the determination(s) made in step606.

It is to be understood that the method of flowchart 600 could beperformed for each port on switch 302 or for only a subset of the portson switch 302.

The foregoing method of flowchart 600 is advantageous because it allowspower management logic 322 to take into consideration the current powerneeds of a device attached to switch 302 when selectively providingpower. This method could be used for example, to turn off power to allports where an IP telephone is attached that is not in use but tocontinue to supply power to IP telephones that are in an active statesuch that they can continue to operate for a fixed period of time (e.g.,2-3 minutes), therefore allowing for a graceful termination of the callby the user. After this, power to even these devices could beterminated. However, this is only one example, and persons skilled inthe relevant art(s) will appreciate that numerous other powerprovisioning schemes may be used based on device state information.

FIG. 7 illustrates a flowchart 700 of a method for selectively providingpower to one or more remote devices by a PoE-capable switch inaccordance with an alternative embodiment of the present invention. Inthe embodiment depicted in FIG. 7, the power management logic within thePoE-capable switch selectively provides power to the one or more remotedevices based both on pre-configured data that associated with a givenport on the switch and on state information obtained for a deviceattached to the port.

The method of flowchart 700 will now be described with further referenceto the elements of network system 300, described above in reference toFIG. 3, although the invention is by no means limited to that particularimplementation.

The method of flowchart 700 begins at step 702, in which powermanagement logic 322 within switch 302 identifies a particular port onswitch 302. At step 704, power management logic 322 accessespre-configured data that is associated with the identified port. At step706, power management logic 322 obtains state information associatedwith a device attached to the identified port.

At step 708, power management logic 322 determines an amount of powerand/or duration that power is to be provided to the device attached tothe identified port based on both the accessed pre-configured data andthe obtained state information. As noted above, with respect to theamount of power to be provided, the remote device may continue toreceive the same amount of power, a lesser amount of power, or no powerat all. With respect to the duration that power is to be provided to thedevice, the remote device may continue to receive power until such timeas UPS 308 can no longer provide power to switch 302, or may receivepower for only a fixed amount of time.

At step 710, switch 302 delivers power to the remote device attached tothe identified port in accordance with the determination(s) made in step708.

The foregoing method of flowchart 700 advantageously allows powermanagement logic 322 to take into consideration both user-providedconfiguration information as well as the current power needs of a deviceattached to switch 302 when selectively providing power. This allows foreven more flexible and sophisticated power management by switch 302.

In each of the foregoing methods 500, 600 and 700, a power supplydetermination is made for a port and then power is supplied to the portin accordance with that determination. In accordance with a furtherembodiment of the present invention, multiple power supplydeterminations may be made for a port over time. Thus, for example, afirst power supply determination for a port may be made at a first timeafter receipt of a notification from the UPS and then a second powersupply determination may be made for the same port at a second timeafter the first time. If the power supply determinations change betweenthe first and second times, then the manner in which power is suppliedto the port will also change. Additional power supply determinations maysubsequently be performed. The power supply determinations may be basedon pre-configured data associated with the port, current stateinformation associated with the device attached to the port, as well asother information such as an amount of time that the UPS has beenproviding power from a secondary source or an amount of power remainingto be supplied to the switch or port.

In one embodiment, power management logic 322 within switch 302maintains an internal timer that is used to determine when a new powersupply determination should be made for the port. The internal timer maytrack an amount of time that has expired since receipt of thenotification by the UPS or since a power savings mode has been enteredby power management logic 322, although these examples are not limiting.When the internal timer has reached a predetermined time limit, a newpower supply determination is made for the port.

An advantage of the foregoing approach is that it allows the powermanagement scheme implemented by POE-capable switch 302 to be adaptedover time to account for changing factors such as the length of timethat the UPS has been running off of secondary power, the amount ofpower remaining for the switch or port, or the state of the deviceattached to the port.

D. Alternate Network Systems in Accordance with an Embodiment of thePresent Invention

In the network system 300 of FIG. 3 and in the associated methodsdescribed in reference to FIGS. 4-7, all power management is handled bypower management logic 322 within switch 302. In these embodiments,remote devices 306 a-306 n are passive in the sense that they do notparticipate in the overall power management function. Rather, each ofdevices 306 a-306 n is provided a certain amount of power for a certainamount of time based on determinations made by power management logic322 alone.

FIG. 8 is a block diagram of a network system 800 in accordance with analternate embodiment of the present invention in which the remotedevices attached to the PoE-capable switch participate in the powermanagement function. As shown in FIG. 8, PoE-capable switch 302 isconnected to a plurality of remote devices 806 a-806 n, each of whichincludes respective power management logic 824 a-824 n. These devicesmay be thin clients, laptop computers, or any other devices that includetheir own power management systems. For example, many laptop computersinclude power management logic that allows the laptop to turn offcertain functions when operating solely on battery power or when thelaptop has gone unused for some predetermined length of time.

In accordance with the embodiment illustrated in FIG. 8, powermanagement logic 322 within switch 302 is configured to communicate withone or more of remote devices 806 a-806 n to cause the power managementlogic within each remote device to implement one or more power savingfeatures.

A method for performing power management in accordance with a systemsuch as network system 800 of FIG. 8 will now be described. Inparticular, FIG. 9 depicts a flowchart 900 of a method for providingimproved power management in a PoE-enabled switch in accordance with anembodiment of the present invention in which the PoE-capable switch andremote devices attached thereto jointly participate in a powermanagement function. Although the method of flowchart 900 will bedescribed with reference to the elements of network system 800, theinvention is by no means limited to that particular implementation.

As shown in FIG. 9, the method of flowchart 900 begins at step 902 inwhich status reporting logic 320 of UPS 308 detects that UPS 308 hasswitched from supplying power to PoE-capable switch 302 from a primarypower source, such as utility-supplied AC power, to a secondary powersource, such as one or more batteries internal to UPS 308.

At step 904, responsive to detecting that UPS 308 has switched fromsupplying power from a primary to a secondary power source, statusreporting logic 320 transmits a notification to PoE-enabled switch 302.At step 906, PoE-capable switch 302 receives the notification from UPS308.

At step 908, power management logic 322 within switch 302 communicateswith one of remote devices 806 a-806 n responsive to the receipt of thenotification in step 906. This communication may comprise one-waycommunication from switch 302 to the remote device or bidirectionalcommunication between switch 302 and the remote device.

At step 910, power management logic within the remote device placesitself in a power saving state responsive to the communication that tookplace in step 908. The power saving state may be any of a variety ofpower saving states available to the remote device based on thecapabilities of the power management logic internal to the remotedevice. For example, the remote device may be able to place itself in apower down mode or a low power mode. The remote device may further beable to place itself in a low power mode by turning off or dimming adisplay associated with the remote device, slowing down a microprocessorinternal to the remote device, switching from high-speed to low-speednetwork communication, or the like. The power savings mode that isentered into by the remote device may be selected by the remote deviceitself or may be selected by switch 302 during the communication thattook place in step 908.

The foregoing method of flowchart 900 is advantageous in that it allowseach remote device to use its own unique power management capabilitiesto conserve power during a period of time when the power supply to thePoE-capable switch is limited or failing. This has the effect ofprolonging the period of time that the PoE-capable switch can operateoff of the limited or failing power supply. Furthermore, this method maybe used in conjunction with the selective power providing methods ofFIGS. 4-7 to increase the power available for critical devices attachedto the PoE-capable switch.

In the embodiments described above, the power management function isimplemented by either a PoE-capable switch alone or by a PoE-capableswitch in conjunction with powered devices attached thereto. FIG. 10depicts a network system 1000 in accordance with a further embodiment ofthe present invention in which the power management function isimplemented in a distributed fashion between a PoE-capable switch 1002and a server 1026 that is capable of communicating with PoE-capableswitch 1002. Server 1026 may comprise a management or administrativeserver, although the invention is not so limited.

In accordance with the embodiment depicted in FIG. 10, any of thefunctions attributed above to power management logic 322 of switch 302(as described above in reference to network systems 300 and 800), exceptfor the actual delivery of power to the remote devices attached to thePoE-capable switch, may be implemented solely by power management logic1028 within server 1026 or jointly by power management logic 1028 withinserver 1026 and power management logic 1022 within PoE-capable switch1002. For example, power management logic 1028 within server 1026 maymaintain all pre-configured data and/or current state related to theports of switch 1002 and the devices attached thereto. This informationmay then be used by power management logic 1022 and/or 1028 to makedeterminations concerning how power is selectively provided to thosedevices.

In accordance with one implementation of the present invention, uponreceipt of a notification from UPS 308, POE-capable switch 1002 sends amessage to server 1026. Upon receipt of the message, power managementlogic 1028 within server 1026 determines how POE-capable switch 1002should selectively supply power to remote devices 1006 a-1006 n. Server1026 then sends instructions to POE-capable switch 1002 based on thisdetermination. Responsive to the receipt of the instructions from server1026, POE-capable switch 1002 selectively supplies power to remotedevice 1006 a-1006 n in accordance with the instructions. However, thisimplementation is described by way of example only. Other methods ofdistributing the power management function between PoE-capable switch1002 and management server 1028 will be readily appreciated by personsskilled in the relevant art(s).

E. Example Uninterruptable Power Supply (UPS) in Accordance with anEmbodiment of the Present Invention

FIG. 11 is a block diagram of a UPS 1100 in accordance with anembodiment of the present invention. As shown in FIG. 11, UPS 1100includes power supply and selection logic 1106 that is connected to bothan external AC power source (e.g., a utility) as well as to an internalbattery 1102. Power supply and selection logic 1106 is configured toselectively output AC power derived from one of these sources to adevice connected to UPS 1100. Power supply and selection logic 1106 isalso configured to provide power derived from the external AC powersource to a battery charger 1104, which operates to charge internalbattery 1102.

In one embodiment, power supply and selection logic 1106 treats theexternal AC power source as the primary source of power and providespower derived from internal battery 1102 only when the external AC powersource is disrupted. In an alternate embodiment, power supply andselection logic 1106 treats internal battery 1102 as the primary sourceof power and provides power derived from the external AC power supplyonly when the power supply from internal battery 1102 is disrupted.

Various aspects of the operation of power supply and selection logic1106 are controlled by control logic 1108. Control logic 1108 is alsoconfigured to communicate information to an external device over a datainterface 1110. Control logic 1108 may be implemented in hardware usinganalog and/or digital circuits, in software, through the execution ofinstructions by one or more general purpose or special-purposeprocessors, or as a combination of hardware and software. Data interface1110 may be any type of standard or proprietary interface forcommunicating data between devices, including but not limited to a wiredinterface such as an RS-232 interface, a USB interface, or an Ethernetinterface, or a wireless interface such as any IEEE 802.11 interface ora Bluetooth® interface.

As shown in FIG. 11, control logic 1108 also includes status reportinglogic 1120. As discussed above in reference to network system 300 ofFIG. 3 and flowchart 400 of FIG. 4, status reporting logic 1120 isconfigured to detect when UPS 1108 has switched from supplying powerfrom its primary power source to its secondary power source and,responsive to detecting this, to transmit a notification to an externaldevice via data interface 1110.

It is noted that UPS 1100 is presented herein by way of example only andis not intended to limit the present invention. Other UPSimplementations will be readily apparent to persons skilled in therelevant art(s) and such other implementations are within the scope andspirit of the present invention. For example, and without limitation,embodiments of the present invention may be implemented using any typeof standby UPS, ferroresonant standby UPS, line-interactive UPS, oronline UPS.

F. Example PoE-capable Switch in Accordance with an Embodiment of thePresent Invention

FIG. 12 is a block diagram of a PoE-capable switch 1200 in accordancewith an embodiment of the present invention. As shown in FIG. 12, switch1200 includes a plurality of ports 1202 each of which is connected tothe other via a switching fabric 1204. Switching fabric 1204 is alsoconnected to control logic 1208. In operation, data units (e.g., packetsor frames) are received and optionally buffered on one or more inputports of ports 1202. Control logic 1208 schedules the serving of dataunits received by these input ports in accordance with a predeterminedscheduling algorithm. Data units are then served to switching fabric1204, which routes them to an appropriate output port among ports 1202based on, for example, a destination address of each data unit. Theoutput ports receive and optionally buffer data units from switchingfabric 1204, and then transmit them on to a destination device.

As also shown in FIG. 12, switch 1200 also includes PoE logic 1206,which is connected to control logic 1208, an external AC power supply,and the plurality of ports 1202. PoE logic 1206 operates under thecontrol of control logic 1208 to supply power derived from the AC powersupply to any of the plurality of ports 1202. Such power is thenprovided to a device attached to the port over the same Ethernet cablethat is used to provide data units to the device. In an embodiment, PoElogic 1206 is configured to comply with the IEEE 802.3af standard,although the invention is not so limited.

As noted above, various aspects of the operation of switching fabric1204 and PoE logic 1206 are controlled by control logic 1208. Controllogic 1208 is also configured to communicate with an external deviceover a data interface 1210 as well as to receive user-provided input,such as configuration data and the like, via a user interface 1212.Control logic 1208 may be implemented in hardware using analog and/ordigital circuits, in software, through the execution of instructions byone or more general purpose or special-purpose processors, or as acombination of hardware and software. Data interface 1210 may be anytype of standard or proprietary interface for communicating data betweendevices, including but not limited to a wired interface, such as anRS-232 interface, a USB interface, or an Ethernet interface, or awireless interface such as any IEEE 802.11 interface or a Bluetooth®interface. User interface 1212 provides a means for a user, such as asystem administrator, to reconfigure the switch and adjust operatingparameters thereof.

As shown in FIG. 12, control logic 1208 also includes power managementlogic 1220. As discussed above in reference to network system 300 ofFIG. 3 and the flowcharts of FIGS. 4-7, in one embodiment of the presentinvention, power management logic 1220 is configured to selectivelyprovide power to one or more of ports 1202 in response to receipt of anotification from a UPS over data interface 1210. Power is then providedfrom the one or more ports to device(s) attached thereto via an Ethernetcable.

In switch 1200, this selective providing of power is carried out bypower management logic 1220 through communication with and control ofPoE logic 1206. The selective providing of power may include selectivelyproviding power to only a subset of the ports, selectively providingdifferent amounts or levels of power to different ones of the ports,and/or selectively providing power for different durations to differentones of the ports. The determination of which of the ports shouldreceive power, the amount of power provided to each device, and theduration over which power is provided to each device may be made bypower management logic 1220 based on a variety of factors or inputs, asdescribed in more detail above.

As further discussed above in reference to system 800 of FIG. 8 andflowchart 900 of FIG. 9, in one embodiment of the present invention,power management logic 1220 is additionally or alternatively configuredto communicate with one or more of the remote devices attached to ports1202 in response to receipt of a notification from a UPS over datainterface 1210. In response to this communication, power managementlogic within the remote device may place itself in a power saving state.

As still further discussed above in reference to system 1000 of FIG. 10,in one embodiment of the present invention, power management logic 1220is additionally or alternatively configured to communicate with a remotemanagement server to carry out any of the various power managementfunctions described herein, except for the actual delivery of power tothe remote devices attached to ports 1202.

It is noted that switch 1200 is presented herein by way of example onlyand is not intended to limit the present invention. Other switchimplementations will be readily apparent to persons skilled in therelevant art(s) and such other implementations are within the scope andspirit of the present invention.

G. PoE-Capable Switch with Power Restoration Capabilities in Accordancewith a Further Embodiment of the Present Invention

The foregoing description focused primarily on power managementtechniques that are performed by a PoE-capable switch (alone or incombination with other entities) in response to receiving a notificationindicating that a power source of the PoE-capable switch is limited orfailing. At some point subsequent to receiving this notification,however, the power source that is limited or failing may be restored. Inaccordance with a further embodiment of the present invention, theentity providing the notification to the PoE-capable switch may providea second notification to the switch indicating that the power source isno longer limited or failing. At this point, the PoE-capable switch mayperform a series of steps to essentially “reverse” the steps that wereperformed after receiving the first notification in order to manage andconserve power.

For example, in response to receiving the second notification, thePoE-capable switch may restore power to remote devices to which itdenied power after receiving the first notification, provide increasedpower to remote devices to which it provided reduced power afterreceiving the first notification, and/or instruct remote devices that itcaused to activate one or more power savings features after receivingthe first notification to de-activate those features. In this manner,the PoE-capable switch can bring all the remote devices to which itsupplies power back into their normal powered states. The order in whichpower is restored to the remote devices may be determined arbitrarily orin accordance with pre-configured priority information and/or currentstate information associated with the remote devices or the ports towhich they are attached.

H. Conclusion

While various embodiments of the present invention have been describedabove, it should be understood that they have been presented by way ofexample only, and not limitation. It will be understood by those skilledin the relevant art(s) that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention as defined in the appended claims. Accordingly, the breadthand scope of the present invention should not be limited by any of theabove-described exemplary embodiments, but should be defined only inaccordance with the following claims and their equivalents.

1. A method for performing power management by a Power over Ethernet(PoE) capable switch, comprising: obtaining current power consumptionstate information from a plurality of remote devices that are connectedto the PoE-capable switch via respective Ethernet cables and thatreceive data and power from the PoE-capable switch via the respectiveEthernet cables; receiving a notification indicating that a power sourceof the PoE-capable switch is limited or failing; and responsive toreceiving the notification, selectively providing power to one or moreof the plurality of remote devices connected to the PoE-capable switchbased on the current power consumption state information obtained fromthe one or more remote devices.
 2. The method of claim 1, whereinobtaining the current power consumption state information from theplurality of remote devices comprises: obtaining information thatindicates whether a remote device is in an active or inactive state. 3.The method of claim 1, wherein obtaining the current power consumptionstate information from the plurality of remote devices comprises:obtaining information that indicates whether a remote device that can beplaced in one of a powered-up, powered-down or standby state is in thepowered-up, powered-down or standby state.
 4. The method of claim 1,wherein receiving the notification indicating that the power source ofthe PoE-capable switch is limited or failing comprises receiving anotification from an uninterruptable power supply (UPS).
 5. The methodof claim 1, wherein selectively providing power to the one or moreremote devices connected to the PoE-capable switch comprises providingpower to only a subset of the plurality of remote devices connected tothe PoE-capable switch.
 6. The method of claim 1, wherein selectivelyproviding power to one or more of the plurality of remote devicesconnected to the PoE-capable switch comprises providing a differentamount of power to different ones of the plurality of remote devicesconnected to the PoE-capable switch.
 7. The method of claim 1, whereinselectively providing power to one or more of the plurality of remotedevices connected to the PoE-capable switch comprises providing powerfor different fixed time periods to different ones of the plurality ofremote devices connected to the PoE-capable switch.
 8. The method ofclaim 1, wherein selectively providing power to one or more of theplurality of remote devices connected to the PoE-capable switchcomprises selectively providing power based also on preconfigured dataassociated with one or more ports of the PoE-capable switch.
 9. Themethod of claim 8, further comprising: obtaining the preconfigured datafrom a remote management server.
 10. The method of claim 1, whereinselectively providing power to one or more of the plurality of remotedevices connected to the PoE-capable switch comprises: making a firstpower supply determination for one of the plurality of remote devicesand selectively providing power to the one of the plurality of remotedevices based on the first power supply determination; and subsequentlymaking a second power supply determination for the one of the pluralityof remote devices and selectively providing power to the one of theplurality of remote devices based on the second power supplydetermination.
 11. A Power over Ethernet (PoE) capable switch,comprising: a plurality of ports, each of the plurality of ports adaptedfor connection to a remote device via a respective Ethernet cable; PoElogic connected to the plurality of ports, the PoE logic controllable toprovide power to selected ones of the plurality of ports for delivery toa remote device connected thereto; control logic connected to the PoElogic and configured to control the operation thereof; and a datainterface connected to the control logic; wherein the data interface isconfigured to receive a notification indicating that a power source ofthe PoE-capable switch is limited or failing, and wherein the controllogic includes power management logic that is configured to obtaincurrent power consumption information from a plurality of remote devicesthat are respectively connected to the plurality of ports and to controlthe PoE logic to selectively provide power to the plurality of portsresponsive to receipt of the notification by the data interface andbased on the obtained current power consumption information.
 12. ThePoE-capable switch of claim 11, wherein the data interface comprises oneof an RS232 interface, a universal serial bus (USB) interface, anEthernet interface, an IEEE 802.11 interface or a Bluetooth® interface.13. The PoE-capable switch of claim 11, wherein the power managementlogic is configured to control the PoE logic to provide power to only asubset of the plurality of ports.
 14. The PoE-capable switch of claim11, wherein the power management logic is configured to control the PoElogic to provide a different amount of power to different ones of theplurality of ports.
 15. The PoE-capable switch of claim 11, wherein thepower management logic is configured to control the PoE logic to providepower for different fixed time periods to different ones of theplurality of ports.
 16. The PoE-capable switch of claim 11, wherein thepower management logic is configured to control the PoE logic toselectively provide power to the plurality of ports based also onpreconfigured data associated with one or more of the plurality ofports.
 17. The PoE-capable switch of claim 16, wherein the powermanagement logic is configured to obtain the preconfigured data from aremote management server.
 18. A method for performing power managementby a Power over Ethernet (PoE) capable switch, wherein the PoE-capableswitch is connected to a plurality of remote devices over respectiveEthernet cables and is operable to provide both data and power to eachof the plurality of remote devices over the same Ethernet cable, themethod comprising: receiving a notification indicating that a powersource of the PoE-capable switch is limited or failing; responsive toreceiving the notification, selecting by the PoE switch at least one ofa plurality of power saving features supported by a selected one of theremote devices and communicating with the selected remote device toindicate to the selected remote device to implement the selected atleast one power saving feature.
 19. The method of claim 18, whereinreceiving a notification indicating that a power source of thePoE-capable switch is limited or failing comprises receiving anotification from an uninterruptable power supply (UPS).
 20. A Powerover Ethernet (PoE) capable switch, comprising: a plurality of ports,each of the plurality of ports adapted for connection to a remote devicevia a respective Ethernet cable; PoE logic connected to the plurality ofports, the PoE logic controllable to provide power to selected ones ofthe plurality of ports for delivery to a remote device connectedthereto; control logic connected to the PoE logic and configured tocontrol the operation thereof; and a data interface connected to thecontrol logic; wherein the data interface is configured to receive anotification indicating that a power source of the PoE-capable switch islimited or failing, and wherein the control logic includes powermanagement logic that is configured to select at least one of aplurality of power saving features supported by a particular remotedevice connected to one of the plurality of ports and to communicatewith the particular remote device to indicate to the particular remotedevice to implement the selected at least one power saving featureresponsive to receipt of the notification by the data interface.
 21. ThePoE-capable switch of claim 20, wherein the data interface comprises oneof an RS232 interface, a universal serial bus (USB) interface, anEthernet interface, an IEEE 802.11 interface or a Bluetooth® interface.